Here is default fan behavior. All numbers taken after ~15 minutes of activity when fan had stabilized. Percent of fan speed followed by GPU temperature according to Catalyst.
24% / 39C - idle, case open
26% / 41C - idle, case closed
33% / 51C - Blu-ray playback, case open
36% / 55C - Blu-ray playback, case closed
52% / 68C - Playing Crysis, case closed.
68% / 75C - Furmark, case closed.
Fan locked at 20% in Catalyst, case closed
41C - idle
58C - blu-ray playback
Ambient temp is 22C.
GPU / memory speed in MHz
Can't hear difference between 20% and 24-26%. Not sure if fan really goes below 26% although Catalyst displays 20%.
For blu-ray playback the difference in temperature between fan locked at 20% and default 36% speed is small. So is audible noise. It looks like 36% is not that much louder than 20-26%. The difference between 52% and 36% is apparent. Fan locking seems to work - with fan locked at 20% temperature raised above 80C quick enough when Furmark is running.
Note that my case doesn't have much airflow for GPU, only vents at the top.
In previous post I tested idle noise in bedroom at night and my house is in quiet area. Now the testing was done in living room during the day - there was some ambient noise of course, nothing loud though.
In this PC I have Corsair HX520W PSU which makes 22 dBA at 0~300W according to SPCR. This is the loudest component in my HTPC. That is until Sapphire fan stays at or below 36%. Noise becomes comparable somewhere between 40 and 45% of Sapphire fan.
At 24-26% fan still can be heard if I move ear ~4-5 inches close to the card. Some quiet crackling noise. At 36% I can hear moving air and a bit of humming. Crackling fades in other noises. At 52% noise becomes louder than power supply. It can be heard from 8-10 feet but it is not that disturbing. Sounds like a decent fan at high speed, nothing exceptional. 64-68% is a bit louder, may sound like a typical PC. Still decent to me. It is Furmark after all. Don't have noise measurement tools and can't describe better.
I could not find any fan controlling utility from Sapphire. Honestly, default fan behavior is good enough for me. If someone gives me a link to some utility I could test it.
I bought this for HTPC because of HD audio and 3D blu-ray and also for some occasional gaming. It is quieter than MSI 8800GT that it replaced and Asus GT240 GDDR5 (this one at low load only) in another PC.
Alternative is probably MSI 460GTX Cyclone which seems to be louder than this Sapphire according to HT4U. Should be so because 460GTX requires more power, two PCIe connectors instead of one.
My typical use - watching HD video 8-10 feet from HTPC is very comfortable. But note that Corsair HX520W does not bother me much, though I can hear it. It's just quiet enough. Now since louder MSI 8800GT is gone I may consider replacing PSU though. MSI 8800GT was not bad either. Was at similar noise level as HX520W during video playback.
So, my resume is - very good card for gaming HTPC.